1. Field of Invention
The present invention relates generally to omnidirectional laser scanners capable of reading bar code symbols in point-of-sale (POS) and other demanding scanning environments.
2. Brief Description of the Prior Art
The use of bar code symbols for product and article identification is well known in the art. Presently, various types of bar code symbol scanners have been developed. In general, these bar code symbol readers can be classified into two distinct classes.
The first class of bar code symbol reader simultaneously illuminates all of the bars and spaces of a bar code symbol with light of a specific wavelength(s) in order to capture an image thereof for recognition and decoding purposes. Such scanners are commonly known as CCD scanners because they use CCD image detectors to detect images of the bar code symbols being read.
The second class of bar code symbol reader uses a focused light beam, typically a focused laser beam, to sequentially scan the bars and spaces of a bar code symbol to be read. This type of bar code symbol scanner is commonly called a “flying spot” scanner as the focused laser beam appears as “a spot of light that flies” across the bar code symbol being read. In general, laser bar code symbol scanners are sub-classified further by the type of mechanism used to focus and scan the laser beam across bar code symbols.
Such flying spot scanners generally employ at least one laser diode, the light from which is focused and collimated to produce a scanning beam. The scanning beam is directed to a scanning element (such as a rotating polygonal mirror or rotating holographic disk), which redirects the scanning beam across a plurality of stationary beam folding mirrors. Light reflected from a bar code label returns to the stationary beam folding mirrors and scanning element. A light collecting optical element collects this returning light and directs it to a photodetector. The electrical signals generated by the photodetector are processed to detect and decode bar code symbols therein.
The bar code symbols are formed from bars or elements typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the code or “symbology” used. The relative size of the bars and spaces is determined by the type of coding used, as is the actual size of the bars and spaces. The number of characters per inch represented by the bar code symbol is referred to as the density of the symbol. To encode a desired sequence of characters, a collection of element arrangements are concatenated together to form the complete bar code symbol, with each character being represented by its own corresponding group of elements. In some symbologies, a unique “start” and “stop” character is used to indicate when the bar code begins and ends. A number of different bar code symbologies exist, including UPC Symbologies, EAN Symbologies, Code 39, Code 128, Code 93, Codabar and Interleaved 2 of 5, etc.
In order to produce a successful scan, an object's bar code symbol must be oriented with respect to a given scanning beam so that the angle therebetween is not so oblique so as to cause an insufficient amount of reflected light to return back to the scanner. Therefore, to achieve a successful scan, the bar code symbol must be positioned sufficiently close to this desired orientation for the given scanning beam.
Thus, to improve the performance of such optical bar code scanners, modern scanners have been developed that employ aggressive scan patterns (i.e., a large number of scanning beams that project into a scan volume at different orientations), which enable such scanners to successfully scan bar code labels over a large number of orientations thereby providing increased scanning throughput. Such modern optical scanners may emit light through a single aperture (such as a horizontal or vertical aperture) or through multiple apertures. Modern optical scanners that emit a large number of scan lines through both a horizontal and vertical aperture are commonly referred to as bioptical scanners. Examples of polygon-based bioptical laser scanning systems are disclosed in U.S. Pat. No. 4,229,588 and U.S. Pat. No. 4,652,732, assigned to NCR, Inc., each incorporated herein by reference in its entirety. In general, bioptical laser scanning systems are generally more aggressive that conventional single scanning window systems scanners in that such systems typically scan multiple scanning beams though the scanning volume and employ a corresponding number of photodetectors for detecting reflection from the multiple scanning beam. For this reason, bioptical scanning systems are often deployed in demanding retail environments, such as supermarkets and high-volume department stores, where high check-out throughput is critical to achieving store profitability and customer satisfaction.
In such modem omnidirectional laser scanning systems, a failed component (for example, failure of a motor that rotates the scanning element, or failure of one or more laser diodes) can be problematic (e.g., lead to a decrease in store profitability and/or customer satisfaction). Yet, the repair of existing omnidirectional scanning systems is a complex, time-consuming undertaking typically requiring a service technician to disassemble the housing (and parts within the housing) to isolate and replace the failed component. Such inefficient scanner repair can also lead to decreased store profitability and/or customer satisfaction (and consequential losses).
Moreover, in the event that a customer requires a different scanner configuration (e.g., for a different scanning application), retrofitting an existing omnidirectional scanning systems is a complex undertaking. Similar to the repair process, typically a service technician disassembles the housing (and parts within the housing) to isolate and replace the components to be reconfigured. Such inefficient scanner reconfiguration repair can lead to increased costs and decreased customer satisfaction.
Similarly, updating a product design to support a different scanner configuration is a complex undertaking involving significant development costs and manufacturing costs.
Thus, there remains a need in the art for improved omnidirectional laser scanning system that can be efficiently and effectively repaired, reconfigured for different scanning applications, and/or effectively configured for different scanning applications at the time of manufacture. Such features will benefit the retailer (lowered costs, better uptime for improved throughput, store profitability and customer satisfaction) and possibly the equipment manufacturer (lowered costs for repair/reconfiguration/configuration and improved customer satisfaction).